you can not use optane as an accelerator on a secondary drive.
https://communities.intel.com/thread/114013
It can only be used on the boot drive.
Are you referring to Intel's proprietary caching, like ISRT?
Because -- I already said in a previous post -- if Optane can be used as an ordinary NVME drive, it can be configured with Primocache to accelerate any drive or combination of drives.
Now I'm looking at the intel forum thread you linked. This confirms my suspicion: Intel won't promote any other options but its proprietary SRT feature, which is a faux-proprietary feature. That discussion is only consistent with SRT as it was originally developed.
The Romex software for a $30 lifetime license, can cache AHCI, NVME and RAID COMBINATIONS from multiple controllers at the same time, if needed. [They
would be "needed," unless a single controller can be configured to provide any combination of those modes at the same time; and I don't think controller BIOSes' work that way.] It is a Swiss-Army-knife of caching features.* It will work in a complex configuration as I suggest, but I'd recommend the KISS principle. You can load up on 32 or 64GB of RAM as you might wish, throw in a 480GB 900P, tie in all the SATA drives whatever the storage mode, "skin that smokewagon and go to work."
You could immediately begin doing as I suggest here by simply buying an Intel 900P PCIE x4 drive-card, preparing it as a cache volume, and installing PrimoCache.
I would think, even so, that as a general purpose desktop powerhouse, unless you're working with very large files on very large disks and very large SSDs, you'd be better with the smaller ~ 250GB 900P and either 16GB or 32GB of RAM. My personal experience with an 8GB RAM cache and a 250 GB NVME, suggests that one could do great with those modest capabilities, for a boot-system disk and maybe 2x 2TB SATA devices.
Another thread started by VirtualLarry has educated me about the 4K random read and write tests on an Optane. That's where the Optane will surpass the performance of a Pro or Evo 960. If it's used as a caching device, you'll get stellar random bench results from a cached HDD that will seem . . . if not supernatural . . . then impressive.
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* Samsung had provided RAPID for its SSD drives through Magician. This, also is proprietary, but nevertheless faux-proprietary. Romex PrimoCache simply replaces RAPID with its RAM-caching feature, which can be added in a two-tiered caching configuration. While it may seem to add complexity, it all works smoothly in combination with an NVME-SSD-caching drive. Nobody would want to use an SATA SSD as a caching drive anymore, but of course you could do what the software had been meant to do before NVME product releases.